This invention relates to new and improved methods and apparatus for the separation and recovery of metal and plastic from plastic insulated wire. Various systems have been utilized in the past for recovering various metals from scrap, and two such systems are shown in U.S. Pat. Nos. 3,749,322 and 3,941,684.
Typically, the scrap, in this case plastic insulated wire, is comminuted into small pieces, typically one-eighth inch in length, by conventional cutting, chopping or granulation techniques. Any magnetic metals can be removed from the mixture by conventional magnetic extraction devices. In the process of U.S. Pat. No. 3,749,322, the chopped pieces are then impact milled producing pieces of bare metal, loose insulation and metal with insulation thereon. The free plastic insulation is removed from the mixture by aspiration leaving metal and plastic covered metal pieces. The cycle may be repeated, with the ultimate hope that all the plastic will be removed from the wire so that after removal of the free plastic, the remainder will be substantially free metal.
In U.S. Pat. No. 3,941,684 the plastic-metal material is chopped or granulated and then passed through an aspirator type separator which produces a light fraction and a heavy fraction. The light fraction is then run through an impact-counterflow separator which removes fiber and dust, with the remainder being mixed with the heavy fraction. This resultant product may be sent to an electrostatic separator for separating metal and plastic.
These prior art processes have several disadvantages. Impact milling or some equivalent is extensively used. There is no provision for separation of insulation from insulation covered wire prior to any impact type treatment. The process of U.S. Pat. No. 3,749,322 is a substantially dry process, and the electrostatic separation of U.S. Pat. No. 3,941,684 requires a substantially dry mixture.
Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for separation of metal and plastic from plastic insulated wire and in particular, process and apparatus wherein a portion of bare metal and a portion of free plastic can be obtained without requiring milling or the like.
Another object of the invention is to provide such method and apparatus utilizing a first separation step for removing bare metal and a second separation step with an eddy current separator for removing free plastic, where the second step may be performed on material which is damp or wet.
These and other objects, advantages, features and results will more fully appear in the course of the following description.